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Sir Nigel Gresley overhaul – Update 21

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Locomotive Engineer Darrin Crone provides us with an insight into recent weeks’ work on the restoration of the great locomotive.

Week commencing 2 October

The valve heads were removed from their spindles last week for machining to suit the new valve liners. Before machining can begin, the ring pegs require removal. These pegs project into the ring grooves to stop the piston valve rings from rotating around the valve head. They are screwed into the valve head, then machined flush with the valve head. A preliminary attempt was made to see if the pegs would unscrew, but unsurprisingly they would not, so we proceeded to drill them out. This was done using the National Railway Museum’s Richmond radial arm drill. By the end of the week they had all been drilled out, but the threaded holes still require clearing of the remains of the peg threads.

The pegs that prevent the rotation of the rings in the valve heads have been drilled out this week. This has to be done very carefully and requires accurate setting up to ensure no damage to the valve head, as they are to be reused.

One of the valve ring pegs after drilling out.

The last of the coupled spring holes were ground out this week. This will assist in the free movement of the spring hanger bolts in traffic as they should not now foul the springs.

The wheelsets returned from re-tyring are now looking very good, as remarked by a number of observers last week. The tyre edges, balance weights and axle ends are now prime painted and we are trialling filling some of the spokes on one of the coupled wheels. We know other locos have had their spokes filled before painting and it does help in cleaning when the loco is back in traffic, as well as looking really good.

Steady progress is being made with the wheelsets. They have now been thoroughly cleaned of the grease and wax used to protect them during their repairs and primer is now being applied.

The lubrication connections to the bogie go through the loco bogie stretcher via screwed-in fittings. The stretcher collects water and this water can find its way onto the bogie bearing surfaces via these connections if they are not a good fit. To ensure a good fit, the top of the stretcher where the fittings seal has been spot faced. When the fittings are replaced they will be sealed with copper washers against the stretcher.

This week NYMR technicians visited us at York to measure the journals of the bogie and coupled wheels so that the finished dimensions of the axleboxes can be determined.

The tender sump was found to be holed when it was removed from the tender tank. This week the bottom plate was cut out and the bottom flange at the centre of the plate recovered. New plate is now on order. We also had a look over the ashpan. It is in a generally sound condition though the side plates are warped near the damper door. Before work can begin we will have to move it to a suitable location from where it is at the moment in the north yard.

The bottom of the tender sump was cut out this week and the flange in the plate recovered. The flange can be seen inside. New plate will be welded in and the old flange re-used.

As riveting around the leading vacuum cylinder stretcher is now complete, the air brake pipe runs in this area can be installed and this was progressed this week. Meanwhile, work continues on cleaning the pipework retrieved from store. The bolting for the flanges on the steel pipework for vacuum and steam heat have been removed and are being cleaned and die-nutted.

The completed vacuum cylinder has been assembled using new seals and the piston checked to ensure free movement. Andy Barwick appears pleased with the results of his efforts.

Much time and effort has been put in to cleaning and preparing pipework for refitting. This pipe is part of the run from the steam chest to the cab. It originally controlled the exhaust steam injector but is now used for the steam chest pressure gauge.

The reverser shaft was fitted last week. This week the pins for the spiral spring and vacuum clutch, both of which are fitted to the shaft, were refitted, greased and finally pinned in place. The lifting arms that go on the end of the shaft were retrieved from store and cleaned.

The repaired leading vacuum cylinder centre bearing was returned to York this week. It was put in place and aligned with the outside bearings using a 2″ diameter pipe. This is the same diameter as the trunnions on the brake cylinders. When in place, the mounting holes for the centre bearing were marked and it was then removed for drilling. After drilling it was refitted and its alignment re-checked, which is very good. The bearings have now been removed. The centre will be painted and the outside bearings will have their bushes renewed.

The leading vacuum cylinder centre bearing bracket was put into correct position this week and the mounting holes drilled to suit. It was then removed for painting. Here it is on the painting bench.

The brake cylinders are now being reassembled with the first, one of the leading 21″ cylinders, completed by closely following the official BR instructions. A test of the piston under gravity showed that it moves satisfactorily.

The staying of the new side plates of the boiler at Llangollen is now complete. This view shows the inside of the firebox. The area of new staying is apparent. The bottom row of stays will be put in after the replacement of the foundation ring.


Week commencing 9 October

The old bushes have now been removed from the leading vacuum cylinder outside bearings but we are still waiting for delivery of material to make up the new bushes. Both leading vacuum brake cylinders have now been reassembled and checked for piston movement. Both are satisfactory and now only require painting. They have now been spot primed.

The overhaul of the leading vacuum brake finished, with only painting now to be completed.

The large trailing loco vacuum brake cylinder is now being prepared for reassembly. Inspection of the cylinder shows that the piston ring has been rubbing and not rolling correctly over a small part of it’s length. We have concluded that this is caused by wear in the bush that guides the piston rod, which has allowed the piston to tilt slightly in the cylinder. Spare bushes are available from spare parts suppliers, but we are yet to confirm the exact size of bush we need, as our 24″ cylinder is unusual (apparently) in having a 1-1/2″ diameter piston rod.

Progress has been made as the new piston ring has been trial fitted to the 24″ piston, and it has been put in the cylinder and inspected for movement. It seems fine with the ring rolling satisfactorily when the piston operates square to the bore.

The steam heat pipework has now been thoroughly cleaned off. The pipework has been inspected and is in very good condition over the front bufferbeam to Cartazzi section. It was then painted in high temperature paint. The first section of pipe under the front bufferbeam was fitted with the air brake pipework in this area, complete with leading air brake valves. This required the removal of the centre section of streamlining behind the front coupling hook.

The air brake piping has been refitted around the front bufferbeam.

By the end of the week the steam heat pipework was refitted back to the Cartazzi. It still requires some final fitting to secure it and there is a joint which will have to be remade. Along the same side of the frames runs the steam chest pipe and this was trial fitted this week. To give us a fixed starting point the outside steam pipe from which it runs was temporarily refitted.

The steam heat pipework was refitted to the loco this week. This view shows behind the front bufferbeam. The pipework for the steam heat still requires securing to all its brackets.

A view from the end of the steam heat pipe at the cab end of the loco frames. The end of pipe can be seen on the right as it snakes up the frames.

Before fitting, the steam chest pipe needed a lot of cleaning as it had a thick layer of carbon adhering to it. The Engineering Team volunteers spending a lot of time doing this while avoiding damaging the soft copper underneath.

All the valve ring pegs have been removed from the valve heads and the threaded holes carefully cleaned up. After final inspection they will be machined to fit the new valve liners.

The piston valve heads have now had all the pegs removed and are ready for machining to suit the new valve liners.

In front of the smokebox, brackets run along the frames to supports a foot plate between the frames. When the loco was dismantled the bracket on the left side was loose and there was evidence that the bracket had been loose and re-tightened repeatedly in the past. When the bracket bolts were removed it was found that the bolt holes were damaged and there was very little clamping area for the bolt head. The holes were repaired this week and new bolts were fitted.

At the other end of the frames work has resumed around the Cartazzi inner frames with cleaning and needle gunning preparing this area for testing and painting.

The platework around the Cartazzi has been given another coat of cleaning and descaling in preparation for final testing as repairs to the inner frames are completed in this area.

Work on the wheels continued this week with primer being applied and our first efforts at filling the surface imperfections in the castings. The filler went on OK and some test sanding was done. This will be continued next week.

The wheelsets continue to be finally cleaned and receive coats of primer. The photo shows the progress so far with one of the bogie wheelsets.

After taking measurements last week the axleboxes are now having bearing material cast on at the workshops of the NYMR at Grosmont.

The handbrake screw from the tender has been condemned as beyond economic repair. To produce a new one we need a suitable drawing. Measurements have been taken so that we can produce a drawing. The drawing we have in our records is different form the screw we have so we visited the NRM archive to look at the drawings they have, and again we could not find a drawing that shows the handbrake screw we have.


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